A system and method for management of bandwidth in a fiber optic, ethernet-based, TDMA communications system. A request/grant process is used to control the use of upstream bandwidth. A sense of time must therefore be shared by a headend and remote end-user devices. The invention provides for a gigabit media-independent interface in a media access controller to detect start-of-frame delimiters in incoming data. This allows for synchronization of a headend and end-user devices. The invention also allows for phase locking a transmit bit rate, at a headend, to the headend's clock. Transmitted data can the be used downstream to derive a local clock. Synchronization can also be maintained by the use of synchronization bytes in MPEG frames and/or variable length frames. Efficient bandwidth usage can also be facilitated by the use of maximum data units in allocating bandwidth in unsolicited grants, and by allowing flexible fragmentation and/or prioritization of internet protocol (IP) packets.
Legal claims defining the scope of protection, as filed with the USPTO.
1. A fiber optic communications system, comprising: a central office; and at least one end-user device in optical communication with said central office, said central office comprising: a physical layer device configured to receive incoming data from said at least one end-user device; a media-independent interface, coupled to said physical layer device, configured to monitor said incoming data to detect a field having a known relationship to a start of a frame; and a media access controller, coupled to said media-independent interface, to determine a time at which the field is observed, relative to an expected time of the field, to determine a ranging offset.
2. The system of claim 1 , wherein said system is an ethernet-based communications system.
3. The system of claim 1 , wherein said system is a time division multiple access (TDMA) communications system.
4. The system of claim 1 , wherein said field is a start of frame delimiter (SFD) byte in a Data Over Cable System Interface Specification (DOCSIS) burst.
5. The system of claim 1 , wherein said field is a specific reference point in a preamble in a Data Over Cable System Interface Specification (DOCSIS) burst.
6. The system of claim 1 , wherein said at least one end-user device is configured to send said incoming data to said central office at an arrival time prescribed by said central office.
7. The system of claim 6 , wherein said incoming data is characterized as being arrived upon detection of said field.
8. The system of claim 7 , wherein said media access controller is configured to determine whether said incoming data arrived too soon relative to said arrival time.
9. The system of claim 7 , wherein said media access controller is configured to determine whether said incoming data arrived too late relative to said arrival time.
10. A fiber optic communications system, comprising: a central office; at least one end-user device in optical communication with said central office; and an aggregating optical node disposed between and in communication with said central office, said aggregating optical node comprising: a physical layer device configured to receive incoming data from said at least one end-user device; a media-independent interface, coupled to said physical layer device, configured to monitor said incoming data to detect a field having a known relationship to a start of a frame; and a media access controller, coupled to said media-independent interface, to determine a time at which the field is observed, relative to an expected time of the field, to determine a ranging offset.
11. The system of claim 10 , wherein said system is an ethernet-based communications system.
12. The system of claim 10 , wherein said system is a time division multiple access (TDMA) communications system.
13. The system of claim 10 , wherein said field is a start of frame delimiter (SFD) byte in a Data Over Cable System Interface Specification (DOCSIS) burst.
14. The system of claim 10 , wherein said field is a specific reference point in a preamble in a Data Over Cable System Interface Specification (DOCSIS) burst.
15. The system of claim 10 , wherein said at least one end-user device is configured to send said incoming data to said aggregating optical node at an arrival time prescribed by said aggregating optical node.
16. The system of claim 15 , wherein said incoming data is characterized as being arrived upon detection of said field.
17. The system of claim 16 , wherein said media access controller is configured to determine whether said incoming data arrived too soon relative to said arrival time.
18. The system of claim 16 , wherein said media access controller is configured to determine whether said incoming data arrived too late relative to said arrival time.
19. An apparatus for fiber optic communications, comprising: a physical layer device configured to receive incoming data from at least one end-user device; a media-independent interface, coupled to said physical layer device, configured to monitor said incoming data to detect a field having a known relationship to a start of a frame; and a media access controller, coupled to said media-independent interface, to determine a time at which the field is observed, relative to an expected time of the field, to determine a ranging offset.
20. The apparatus of claim 19 , wherein said field is a start of frame delimiter (SFD) byte in a Data Over Cable System Interface Specification (DOCSIS) burst.
21. The apparatus of claim 19 , wherein said field is a specific reference point in a preamble in a Data Over Cable System Interface Specification (DOCSIS) burst.
22. The apparatus of claim 19 , wherein said at least one end-user device is configured to send said incoming data to said apparatus at an arrival time prescribed by said apparatus.
23. The apparatus of claim 22 , wherein said incoming data is characterized as being arrived upon detection of said field.
24. The apparatus of claim 23 , wherein said media access controller is configured to determine whether said incoming data arrived too soon relative to said arrival time.
25. The system of claim 23 , wherein said media access controller is configured to determine whether said incoming data arrived too late relative to said arrival time.
Cooperative Patent Classification codes for this invention. Click any code to explore related patents in that topic.
March 19, 2009
July 5, 2011
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